There are a variety of natural family planning (NFP) methods available today that differ in algorithm and biomarkers used to identify women's fertile window. This study will directly evaluate the NFP system known as the Creighton Model FertilityCare System (CrM). The Creighton Model System is a well-established educational system about fertility which involves no devices. The CrM teaches women a standardized way of observing and describing their vaginal discharge each day during routine use of the bathroom, and interpreting the changes in vaginal discharge to determine whether they are likely to be fertile that day or not. Vaginal discharge changes as tracked by the CrM are an accurate indicator of the changes in secretions from the uterine cervix that relate to the approach of ovulation.